Within the power industry, valves are operated remotely from open, closed and intermediate positions to improve or maintain utility power plant output, or in many cases to provide for the protection of the general public from release of radioactive materials either directlyor indirectly. Continual, proper operation of these valves is essential to the well-being of the industry and the general public. The extreme emphasis on safety in nuclear power plants (and the presently bad reputation of the nuclear industry) has put a premium on the importance of maintaining proper operation of valves, of which there may be hundreds within a single plant.
At the forefront of industry attempts to monitor and maintain proper operation of these critical valves is the recent invention of Arthur G. Charbonneau, et al described in U.S. Pat. No. 4,542,649 (hereinafter referred to as "649"). The 649 invention disclosed a new and important valve operator and monitoring system to measure, record and correlate valve stem load, limit and torque switch positions, spring pack movement and motor current providing time related information on valve performance. The information made available by the 649 patent provides a direct indication of developing valve and operator problems such as excessive or inadequate packing load, excessive inertia, proximity to premature tripping, incorrectly set operating limit and torque switches, improperly functioning thermal overload devices, inadequate or excessive stem thrust loads, gear train wear, stem damage, and load relaxation.
The prior 649 patent discloses a particular spring pack movement monitoring device to monitor the linear motion of the operator spring pack as one part of the information collection function of that invention. The 649 spring pack movement monitoring device makes use of an extension rod pressed against one end of the spring pack compression shaft (or thrust shaft) and held against the spring pack shaft by a tension system. The extension/rod device system of the 649 patent relies upon the extension rod contacting an element of the spring pack which moves in both (opposite) lineal directions in direct response to movement of the operator worm. The 649 spring pack movement monitoring device has, apparently, very valuable application when access can be had to the end of the operator spring pack. However, the present inventors recognize that not all valve operators grant easy or practical access to the end of the spring pack and, thus, the extension rod and tension device assembly of the 649 specification will not work on all valve operators. An example of just such an uncooperative valve operator is that made by Jouvenel, and known as their L-type operator.